1907.] NATURAL SCIENCES OF PHILADELPHIA. 117 



levators. These are composed of but one or two fibres apiece. The 

 first of these muscles, tlie protractors (fifj. 5. pro.pr.), lie close together 

 near the midline, beneath the proboscis. They are attached to the 

 ventral body wall, just inside of the attachment of the median ventral 

 lonfjitudinal muscles. From here they pass directly backwards, and 

 arc inserted on the ventral side of the proboscis about midway of 

 its length. At their attachment and insertion these, as well as the 

 other proboscis muscles, display the brushlike tufts, formed by 

 division of the fibrils, that were observed in the case of the trunk mus- 

 cles. The second pair, the fl.exors (fig. 4, pro.f.), join together the 

 two ends of the proboscis, passing over its convex anterior face. The 

 retractors (fig. 4, pro.r.) are attached to the ventro-lateral portion 

 of the horizontal limb of the oesophagus, above the proboscis, and 

 descend to their insertion in its anterior portion. The levators are 

 attached to the lateral body wall and inserted on the sides of the 

 proboscis, near its middle. 



The stomach is a cylindrical or l^arrel-shaped organ, occupying the 

 body cavity from the anterior limits of the third trunk segment to the 

 middle of the fourth. These two segments, it will be remembered, 

 far exceed the others both in length and diameter, so that the stomach 

 is therefore a relatively large organ, its length being nearly one-half 

 that of the trunk. Its diameter approaches that of the body cavity 

 of the segments in which it lies; the space that remains between the 

 stomach and body wall being reduced to a narrow cleft. The anterior 

 end of the stomach is more or less distinctly truncate; its posterior 

 end, on the other hand, is conical, tapering to join the intestine. This 

 jimction, like that with the oesophagus, is dorsal to the median axis. 



The stomach wall (figs. 6 and 35) is from 11 // to 30 /f in thickness, 

 and composed of a uniform layer of cuboid or low columnar cells, 

 whose inner ends bear long cilia. Each cell displays at its central end 

 a shallow layer of homogeneous protoplasm, staining deeply in iron- 

 hajmatoxylin after fixation b}' sublimate, less densely after Flemming's 

 mixture; just below this layer are the close-set basal knobs of the cilia. 

 The body of the cell consists of dark staining and much vacuolated 

 cytoplasm, within which, usually near the base of the cell, is an ovoid 

 or spherical nucleus, provided with the usual karyosome. The 

 cytoplasm of the cells of the stomach presents a somewhat varied 

 appearance, according to the fixative employed. Sections cut from 

 material fixed in corrosive sublimate (fig. 6) show the cytoplasm much 

 vacuolated, indeed so much so that the protoplasm is reduced to 

 scarcely more than a coarse and densely staining reticulum. Within 



